Volume holographic diffusers

ABSTRACT

A collimated or partially collimated light beam is sent through a substrate matrix of a plurality of nested individual joined geometrically shaped cells wherein each of the cells contains a patterned volume holographic diffuser which produces a transmitted diffused light beam from each of the cells and then superimposes each transmitted diffused light beams from each of the cells to produce a combined resultant diffused light beam. The geometrically shaped cells are clustered in a contiguous arrangement of nested cell subgroups, which are themselves geometrically shaped. When graphed, an angular luminance distribution profile curve with sharply vertical profile slopes at halfpeak points and with a substantially flat and wide peak is resultant which produces a uniform resultant luminance over a wide range of view with a predetermined beam spread and beam deflection angle in relation to a predetermined location of view of the combined resultant diffused light beam.

RELATED PATENTS AND APPLICATIONS

This application is based upon, and claims priority benefits of, U.S.Provisional Application No. 60/175,001, filed Jan. 7, 2000.

FIELD OF THE INVENTION

This invention relates generally to volume holographic diffusers.

BACKGROUND OF THE INVENTION

Holographic diffusers are well known in the art. Additionally, LCDdisplays, which make use of holographic diffusers, are also well knownin the art. Typically, an LCD display uses a holographic diffuser eitherto augment the back lighting of the LCD display or to direct thetransmitted display light to an observer located within a particularrange of viewing angles. To accomplish this the holographic diffuserdirects the diffused light in particular paths of propagation designedto fill a specific range of viewing angles.

For example, if an aircraft cockpit display has a holographic diffuser,the head box of the pilot will be the area that could be occupied by thepilot's eyes from which the pilot can be expected to view the output ofthe display. Therefore it is advantageous to design the holographicdiffuser to direct the light transmitted by the LCD display to the headbox of the pilot. Thus, it is known to redirect light using holographicdiffusers.

However, it is difficult to maintain uniform luminance over the desiredrange of viewing angles and to produce a sharp luminance fall-off at theedges of the viewing angle range. This difficulty exists because eachholographic diffuser design causes display luminance to be a variablefunction of viewing angle. As a result, display luminance can varydetrimentally when viewed from within the pilot's head box and theluminance cut-off at the fringes of view lacks sharpness. This isgenerally attributable to two undesirable properties of knownholographic diffusers. Firstly, as the light's angle of incidence on aholographic diffuser approaches the limits of acceptable angles ofincidence consistent with its design, the hologram's diffusionproperties begin to break down and the incident light begins to transmitthrough the hologram without becoming diffused or deviated inpropagation angle. Secondly, the corresponding plot of display luminanceas a function of viewing angle resembles a bell-shaped curve. Thiscauses the viewed display images to become dim as viewing anglesapproach the edges of the viewing angle range. Further, considerablewasted light falls outside the useful range of viewing angles owing tolack of sharpness in luminance fall-off at the fringes of the viewingangle range of interest.

FIG. 1 is a side view of a conventional diffusion screen arrangement inthe art. With reference to FIG. 1, a collimated, or partiallycollimated, white light input beam 10 illuminates a refractive mediumsubstrate 12 and a volume holographic film diffuser 13 at normalincidence. The holographic film 13 diffuses the projected output beam 14over angular range λ. The angle λ shown in FIG. 2 is the halfpeak fullwidth angle of the luminance angular distribution profile betweenhalfpeaks 20. Little, or no, color dispersion is noticeable.

Referring to FIG. 1A, it is noteworthy that when a collimated, orpartially collimated, white light input beam 10 is incident onrefractive medium substrate 12 at an angle φ greater or less than 90°,the beam exiting the volume hologram can be designed to maintain thesame (or nearly the same) diffusion angle, λ, as that for normalincidence. Alternatively, referring to FIG. 1B, with normal incidence ofcollimated, or partially collimated, white light input, an output beamwith a diffusion angle, λ, can be projected in a direction that is notnormal to the substrate. This can improve the luminance of an aircraftcockpit instrument display located below the pilot eye level, and withthe instrument display face normal at a considerable (20° to 30° ormore) angle to the pilot's direct view line. This can be accomplished byprojecting the diffused output beam away from the instrument face normaland toward the center of the pilot's head box.

Also, designs of volume holographic diffusers are possible in which theinput white light collimated, or partially collimated, beam and thepropagation direction of the diffused output beam both deviate from thesubstrate (or instrument display face) normal.

In these prior art diffuser designs, the gradual luminance fall-off atthe fringes of the viewing angle range (and at angles beyond thosefringes) causes a waste of light resulting in reduced display luminance.Therefore, to minimize wasted light and maximize the light flux capturedwithin the viewing angle range of interest, it is advantageous tomaximize the slope at the halfpeak points of the luminance angulardistribution curve.

SUMMARY OF THE INVENTION

This invention is particularly useful as a beam deflecting diffusionscreen for displays, such as LCD instrument panel modules in aircraftcockpits and heads-up displays although its application is not limitedto displays. A set of narrow superimposed deflected diffused beamprofiles with sharp luminance cut-offs at their halfpeak full widthpoints forms a composite angular luminance distribution. Byconcentrating these superimposed light beams that project from a displaypanel and by capturing them within the pilot's head box, efficiency isimproved by minimizing the light wasted by projection outside thepilot's head box. Although an individual projected narrow beam angularprofile does not, by itself, render the display luminance uniform as afunction of viewing angle, the superposition of a plurality ofindividual narrow beams can be designed to generate uniform luminanceover a wide viewing angle range of interest.

The invention is accomplished with the structure and method of thepresent invention by sending collimated, or partially collimated, lightthrough a substrate with a film matrix comprising a nested plurality ofindividual joined geometrically shaped holographic cells. The cellscomprising the matrix are subdivided into groups. Each cell within agroup contains a uniquely patterned volume holographic diffuser. Thisgenerates a diffused narrow light beam projected in a direction diversefrom that projected by every other cell in the group. The superpositionof the variously directed diffused narrow light beams projected fromeach cell group produces a combined resultant diffused wide light beam.The resultant light beam has a luminance angular distribution profilewith sharply vertical slopes at its halfpeak points and a substantiallyflat and wide peak over a wide viewing angle range of interest. Thedisplay luminance thus produced is uniform over a wide range of viewingangles. This range of angles is centered on a specific beam deflectionangle that passes through the midpoint of the pilot's head box. Thus thematrix of cells on the display produces a uniform luminance over theentire surface of that display and when viewed from any point within thepilot's head box. The resulting display luminance is substantiallyuniform over a wider range of viewing angles than is known in the artand the sharpness of the luminance fall-off at the angular distributionprofile halfpeak points is greater than is known in the art. In thepreferred embodiment, a non-alternating, single image is also providedfor both eyes rather than alternating a separate right eye image with aseparate left eye image.

This invention is most useful for applications where collimated, orpartially collimated, light is incident on a display and a need existsto project the light transmitted by the display into a wider and morediffuse beam. A further enhancement of its usefulness occurs when theprojected diffuse beam is uniformly distributed over a desired widerange of viewing angles and with sharp luminance cutoffs at the edges ofthat range. The projected diffuse beam can also have an asymmetric (i.e.different angular widths in orthogonal profile planes) output beamenvelope, which has a high efficiency and little or no color dispersion.It may also be desired to have the option of deflecting the axis of thisoutput beam envelope at a different angle from the input beam direction.An asymmetric output beam envelope and/or one having an axis differentfrom that of the input beam is useful for minimizing light flux thatfails to fall within a pilot head box having asymmetric dimensionsand/or one that is positioned away from the display normal.

By creating a matrix of volume holographic cells arranged in a regularpattern on or within the surface of the diffusion screen, the adjacentcells of a subgroup of the matrix have different holographic designseach of which deflects the diffused beam projected therefrom in adifferent direction. The beam spread and deflection direction of eachprojected output beam can be controlled by means of each differentsubgroup cell holographic design. The superposition of diffusedprojected output beams thus produced generates a composite angularluminance distribution with sharp profile slopes at its halfpeak pointsand a substantially flat wide peak. The composite projected beam has thedesired diffusion spread and propagation direction.

Thus, the present invention uses a method and apparatus for sendinglight beams from a display through a substrate matrix of nestedindividually joined geometrically shaped cells. The cells are dividedinto subgroups wherein each cell of a subgroup contains a patternedvolume holographic diffuser with a different design or projection anglefor optimal diffusion to occur. Each cell of a subgroup projects adiffused light beam with a different angle of propagation from that ofthe other cells of the subgroup.

Owing to the holographic diffuser's repetitive pattern of cellsubgroups, there are many more cells than beam projection directions.Therefore each cell has a beam projection direction shared with manyother cells in the matrix. The angular distribution of light incident ona holographic diffuser cell can be widened by the cell's diffusionproperties. Thus the angular distribution of the beam projected fromthat cell can be wider than that of the incident light beam. Further,the beam projected from that cell can propagate in directions diversefrom that of other cells of its cell subgroup. Therefore the angulardistribution of the composite beam projected from a subgroup of cellscan be wider and, possibly more angularly asymmetric, than any of theindividual component beams comprising the composite beam. Further,because the composite beam can be comprised of a plurality of individualbeams having narrow angular distributions (compared with the compositebeam's distribution), the annular distribution profile slope at thecomposite beam's halfpeak points can be sharp and nearly vertical,similar to that of the narrow beams. When the display is viewed frompoints in the pilot's head box, display luminance can be a uniformfunction of viewing angle because the peak composite projected beam'sangular distribution is substantially flat over a wide range of viewingangles. Thus a predetermined beam spread and deflection angle is createdin relation to the viewer. Photometric efficiency is maximized by virtueof high, nearly vertical, slope angles produced at the fringes of theluminance angular distribution profiles projected from cell subgroupsacross the display surface.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a prior art diffusion screen arrangement.

FIG. 1A is a side view of a prior art holographic diffuser wherein theincoming angle incidence of input light is not normal to the face of theholographic diffuser.

FIG. 1B is a side view of a prior art holographic diffuser wherein theoutputted light is not normal to the surface of the holographicdiffuser.

FIG. 2 is a profile plot in Cartesian coordinates showing the prior artbell curve function of luminance verses viewing angle for a specificprojection angle.

FIG. 3 is a perspective view of the input side of the holographicdiffuser of the present invention.

FIG. 4 is a perspective view of the output side of the holographicdiffuser of the present invention.

FIG. 5 is a perspective view of the holographic diffuser of the presentinvention wherein 18 sided cell subgroup shapes are used.

FIG. 5A depicts the nested holographic cells of a cell subgroup of FIG.5.

FIG. 6 is perspective view of the holographic diffuser of the presentinvention wherein rectangular holographic cell subgroup shapes are used.

FIG. 6A depicts the nested holographic cells of a cell subgroup of FIG.6.

FIG. 7 is perspective view of the holographic diffuser of the presentinvention wherein triangular holographic cell subgroup shapes are used.

FIG. 7A depicts the nested holographic cells of a cell subgroup of FIG.7.

FIG. 8 is a graph in Cartesian coordinates of resultant luminance versusprojection angle for three superimposed diffusion profiles of thepresent invention when partially collimated light is input to aholographic diffuser.

FIG. 9 is a graph in Cartesian coordinates of resultant luminance versusprojection angle for two superimposed diffusion profiles of the presentinvention when partially collimated is input to a holographic diffuser.

FIG. 10 is a graph in Cartesian coordinates of resultant luminanceversus projection angle for two superimposed diffusion profiles of thepresent invention when collimated light is input to a holographicdiffuser.

FIG. 11 is a side view of the first element of the second embodiment ofthe present invention.

FIG. 12 is a side view of the complete second embodiment with bothelements in place.

DETAILED DESCRIPTION

FIGS. 3 and 4 show a holographic diffuser 30 in accordance with presentinvention. Referring to FIG. 3, the holographic diffuser 30 is made upof nested individual joined geometrically shaped cells that form amatrix of cells disposed across holographic diffuser 30. These cells areclustered in a contiguous arrangement of nested cell subgroups 301 thattogether form the patterned holographic diffuser 30. Each individualjoined geometrically shaped cell of cell subgroup 301 comprises anindividual patterned holographic diffuser element. Each holographicdiffuser element of a cell subgroup diffuses the input light andprojects the diffused beam in a direction unique from that projected bythe other diffuser elements of its cell subgroup. A display 1, which maybe typically a backlit LCD display is shown in FIG. 3. Incident light 2comprised of light rays 5 having various directions of propagation fromthe display 1 are incident upon holographic diffuser 30.

It is noted that the distance between display 1 and holographic diffuser30 is not drawn to scale, and in practice the closer the display is tothe diffuser, the easier it is to produce a clear image withoutresolution loss. Therefore, it is preferred that holographic diffuser 30be laminated or attached to display 1.

In order to prevent resolution loss by the holographic view screen 30,the size of the subgroup 301 of holographic cells must be smaller than adisplay pixel. As a rule of thumb, a subgroup dimension should notexceed half the corresponding pixel dimension. Thus the area of thesubgroup should not exceed ¼ the area of a display pixel.

Further, those skilled in the art will realize that edge effects at theboundary between adjacent holographic cells may prevent the desirableabrupt “step function” change of holographic properties in thetransition region between cells. Therefore, a loss of holographicperformance occurs in the boundary area between two cells. This loss ismore pronounced for smaller holographic cells owing to the greaterpercentage of the cell area occupied by the transition region betweensmaller cells. Accordingly, the area of the holographic cells comprisinga subgroup 301 should be made no smaller than required to preventresolution loss.

In FIG. 3, partially collimated light 2 incident on holographic diffuser30 passes through its multiple cell structure. Each individual nestedholographic element of this structure diffuses the light it interceptsand projects it toward some portion of the pilot's head box. Each cellcomprising a cell subgroup 301 projects its diffuse beam in a directiondiverse from the other cells of that subgroup. The superposition of allthese diversely projected beams form a composite beam that can be viewedfrom all points within the pilot's head box. The luminance versusviewing angle plot of FIG. 8 is an example of the luminance of asubgroup of cells as a function of viewing angle for observation pointswithin the pilot's head box. Note that FIG. 8 is a profile plot takenthrough a three-dimensional plot representing two orthogonal angulardimensions (representing directions of light flux propagation passingthrough the area of the pilot's head box) and the luminance dimension.Accordingly, there could be a three-by-three array of diffused beamsprojected at different projection design angles from a subgroup of nineholographic cells. The plot of FIG. 8 could be a profile slice takenthrough three of the nine projected beams. The three dashed line plots80 of FIG. 8 represent luminance angular profiles of individualprojected beams, each centered on its unique projection design angle.The solid line 83 represents the composite sum of the individualprojected beam luminance angular distributions 80.

Note that each beam plot crosses the adjacent beam plot at the commonhalf peak point of both beams. This condition, necessary to produce auniform luminance function of viewing angle, is implemented by selectingthe angular separation of projection design angles of the individualbeams to be equal to the angular separation of their half peak points.

The profile plot of a three-by-three arrangement of diffused beamsillustrated by FIG. 8 is one of many possible arrangements. FIG. 9 is anexample of a profile plot through the center of a pair of projectedbeams that could be in a one-by-two, a two-by-two, a three-by-two, orany N-by-two arrangement of beams projected from a holographicdiffuser's cell subgroup 301. Of course, there are also many otherpossible arrangements, such as three-by-four, three-by-five,four-by-four, or in general, N-by-M, where the N and M variables couldbe any integer value within reason.

A portion of the diffused beams 305 meet at a location 100 (shown inFIG. 4 as the eye location of the viewer) which is within a designatedspatial region such as a pilot's head box. These portions of diffusedbeams are individual viewing angles from the eye location 100 to each ofa plurality of cell subgroups 301 on the holographic diffuser 30. Atlocation 100, the diffused beam portions projected along viewing angles305 are superimposed.

The superimposed beam portions are shown graphically as an outputangular distribution profile curve in FIG. 8 by curves 80 that, addedtogether, form the desired curve 83. By virtue of the uniform luminanceover the wide range of viewing angles in FIG. 8, the display luminancefor viewing angles 305, which are within that uniform luminance angularrange, is also uniform. Accordingly, the luminance of the display isoptimized at viewing location 100. Additionally, the wasted lightoutside the viewing angle region of interest of a traditionalholographic diffuser is overcome by curve 83, which has a nearlyvertical slope at halfpeak points 82.

This improvement is illustrated by comparing FIG. 8 with FIG. 2. In thepresent invention, it is readily seen from FIG. 8 that the luminance inthe vicinity of the halfpeak points increases or decreases in a verysharp fashion. This is in contrast to the prior art FIG. 2 wherein theluminance is more of a bell curve shaped function having a relativelysmall angular region of uniform luminance and a more gradual variationof luminance in the angular vicinity of the halfpeak points. Theresulting wasted light flux is undesirable in a display because itreduces the angular viewing range of adequate luminance. This phenomenonis generally referred to in the art as “the low slope problem at thehalfpeak point”.

Referring again to FIGS. 3 and 4, the adjacent nested holographic cellsubgroups 301 can be implemented in an endless variety of nestedgeometric shapes. Three examples of these are illustrated in FIGS. 5, 6,and 7. FIG. 5 illustrates a holographic diffuser 50 comprised of anested matrix of 18-sided polygonal cell subgroups 501. FIG. 6illustrates a holographic diffuser 60 comprising a nested matrix ofrectangular cell subgroups 601. FIG. 7 illustrates a holographicdiffuser 70 comprising a nested matrix of triangular cell subgroups 701.

Each of these subgroup shapes is filled with a nested matrix ofholographic cells. Examples of these are illustrated in FIGS. 5A, 6A,and 7A. FIG. 5A shows how seven nested hexagonal holographic cells 502can fill cell subgroup 501. FIG. 6A shows how nine nested rectangularholographic cells 602 can fill rectangular cell subgroup 601. FIG. 7Ashows how sixteen nested triangular holographic cells 702 can filltriangular cell subgroup 701.

Each different geometric shape has as its own holographic lightdistribution properties which contribute to the goal of widening theresultant diffused beam in an angularly uniform luminance distributionand with minimum waste outside the angular region of interest to enablethe invention.

Nesting of the cell subgroups and of the cells comprising them isadvantageous because gaps between subgroups, or between the cells thatcomprise them, would create void areas having no holographic diffusionproperties. Light leakage through said void areas would cause eitherlight losses or unwanted non-uniform display luminance owing tonon-uniform diffusion properties.

The holographic properties of cell subgroups and the cells that comprisethem differ. The holographic properties of each cell subgroup areidentical to those of every other cell subgroup of the holographicdiffuser. This ensures identical diffusion characteristics for thecomposite beam projected from each cell subgroup. The holographicproperties of the holographic cells comprising each cell subgroup differfrom each other. This is necessary for increasing the prior artdiffusion angle 14 defined in FIGS. 1, 1A, and 1B. In addition, aspreviously described, this is necessary for obtaining luminanceuniformity over the design range of viewing angles.

FIG. 10 is an example of the combined luminance angular profile obtainedwhen collimated light is input for a hologram diffusion screen designedfor partially collimated light, such as that for which the luminanceangular profile is illustrated in FIG. 9. The distribution cells in FIG.9 have design angles differing by an amount that causes the twoluminance angular profiles cross at a common luminance half peak point.This ensures that the luminance angular distribution profile for thecombination, or superposition, of the two luminance distributionprofiles projected from the two cells is nearly uniform between the twoholographic cell design angles. However, when the two cells areilluminated by more collimated light than that for which their designangles were configured, the resulting distribution profiles 150illustrated in FIG. 10 will be narrower than those of FIG. 9.Accordingly, the individual luminance profiles 150 of FIG. 10 fail tocross at a common half peak point thereby generating a combinedluminance profile with a deep luminance valley between the two luminanceprofiles 150. The resulting luminance angular non-uniformity in FIG. 10can be remedied by redesigning the holographic diffuser to have asufficiently small angular separation between the projection designangles of the two cells to make its two individual luminance profilescross at a common half peak point. In this way it is possible also todecrease wasted light and to maintain luminance uniformity forcollimated, or nearly collimated light input. This will produce uniformdisplay luminance over a larger angular viewing range in comparison tothe prior art which fails to use a multiplicity of individually joinedgeometrically shaped cell subgroups 301 or a superposition of thediffused outputs beams of such cell subgroups.

Specifically, again referring to FIGS. 3 and 4, and as noted above, thepresent invention creates a holographic diffuser 30 that has a patternof holographic cell subgroups 301 distributed over the face of thediffuser and/or within the substrate. If the nested adjacent cellswithin each cell subgroup 301 have different holographic diffuserdesigns, then a collimated or partially collimated white (or monochrome)light beam input can generate a superposition of two or more diffuseroutput beam angular distributions (see FIG. 8 and FIG. 9). This isaccomplished by generating output diffusion beams in at least twodifferent directions.

The present invention is therefore able to function with both collimatedand partially collimated light because each cell produces a superimposedresultant image at viewing location 100 resultant from a sum of diffusedbeams at projected at different angles. This results in the compositeoutput distribution 83 of FIG. 8 from its components of narrow outputdistributions 80. This also makes it possible to redirect diffused lightbeams to fill a viewing angle range of interest when the incident light5 is normal to the diffuser 30 as shown in FIG. 1B or when it is notnormal to the diffuser 30 as shown in FIG. 1A.

It is known in the art that backlighting an LCD display with collimatedor partially collimated light considerably improves the contrast of saiddisplay. However, the greater the backlight collimation, the moredifficult it becomes for current art diffusion screens to illuminate awide range of viewing angles uniformly and efficiently (withoutsignificant wasted light flux). This invention utilizes collimated, orpartially collimated, backlighting to enable the simultaneousimprovement of display contrast, uniformity, and efficiency over thatprovided by current art view screens for a wide range of viewing angles.

Thus overall, the invention improves angular uniformity, which is theluminance uniformity of any cell subgroup in the matrix as a function ofviewing angle.

A second embodiment of the present invention uses two or more volumeholographic diffusers to diffuse passed light that was not diffused in afirst pass through a first holographic diffuser as discussed in detailbelow.

Another property of volume holographic diffusers is the tendency tobecome transparent, i.e., to become non-diffusing transmitters, when theincident beam direction differs sufficiently from its design projectionangle. This property is illustrated by FIG. 11. In particular, referringto FIG. 11, incident beam 5 is diffused by the diffuser 30 to creatediffused beam 7. Beam 5 a is incident at an angle relative to theprojection angle, and as discussed above, beam 5 a is transmittedwithout being diffused by the diffuser. It is also noted that inputbeams 5 and 5 a are spatially separated for illustration purposes. Thebeams should, in practice be superimposed on the same area or across theentire substrate 30.

However, as shown in FIG. 12, in order to eliminate the non-diffusetransmitting property of beam 5 a incident at an angle relative to theprojection angle, a second volume holographic diffuser 30 can be addedto the first. The second added holographic diffuser 30 a can beair-spaced from the first holographic diffuser 30. Preferably, it wouldbe laminated to the first holographic diffuser 30. This would inhibitFresnel reflection losses and, owing to the larger gap between thedisplay and the diffusion screen that would exist with an air gap,resolution losses. The second holographic diffuser 30 a would bedesigned to diffuse the beam 5 a that was transmitted non-diffusely bythe first holographic diffuser 30. The second holographic diffuser 30 awould also transmit most parts of the diffusion profiles due to thefirst beam 5. The parts of the first beam's diffusion profile, which areclosely aligned with the second beam's angle of incidence, would undergoa second stage of diffusion. Also, the designs of both holograms woulddepend on whether or not the interfaces between them are laminated orair-spaced.

Further, more than two holographic diffuser layers, may be used toaccommodate an even larger range of input beams angles to be diffused.Also, the axes of symmetry of the diffusion profiles need not bedesigned to be parallel to the corresponding input beams.

The present invention is not to be considered limited in scope by thepreferred embodiments described in the specification. Additionaladvantages and modifications will readily occur to those skilled in theart from consideration of the specification and practice of theinvention.

What is claimed is:
 1. A method of diffusing light for a displaycomprising the steps of: sending a group of collimated or partiallycollimated light beams through a substrate matrix of a plurality ofnested individual joined geometrically shaped cells wherein each of thecells contains a patterned volume holographic diffuser with a setprojection angle; producing from each of the cells a transmitteddiffused light beam with a narrow angular luminance distribution profilecurve with sharply vertical profile slopes at halfpeak points; andsuperimposing each transmitted diffused light beam from each of thecells to produce a combined resultant diffused light beam having anangular luminance distribution profile curve with sharply verticalprofile slopes at halfpeak points and with a substantially flat and widepeak to produce a uniform resultant luminance over a wide range of viewangles with a predetermined beam spread and beam deflection angle inrelation to a predetermined location of view of the combined resultantdiffused light beam.
 2. The method of claim 1 wherein the step ofsending the group of collimated or partially collimated light beamsthrough a substrate matrix sends each light beam at an angle ofincidence which is not normal to an input surface of the substratematrix of the plurality of nested individual joined geometrically shapedcells.
 3. The method of claim 1 wherein the step of superimposing eachtransmitted diffused light beam from each of the cells to produce acombined resultant diffused light beam produces the combined resultantdiffused light beam at an angle of view which is not normal to the inputsurface of the substrate matrix of cells.
 4. The method of claim 1wherein the nested individual joined geometrically shaped cells arerectangular in shape.
 5. The method of claim 1 wherein the nestedindividual joined geometrically shaped cells are square in shape.
 6. Themethod of claim 1 wherein the nested individual joined geometricallyshaped cells are triangular in shape.
 7. The method of claim 1 whereinthe nested individual joined geometrically shaped cells are hexagonal inshape.
 8. The method of claim 1 wherein: the nested individual joinedgeometrically shaped cells arc polygonal in shape.
 9. The method ofclaim 1 further comprising the steps of: providing an additionalsubstrate matrix having patterned individual joined geometrically shapedcells of holographic diffusers with set projection angles structured forforming a combined resultant diffused light beam with an angularluminance distribution profile curve with sharply vertical profileshapes and with a substantially flat and wide peak to produce a uniformresultant luminance over a wide range of view with a predetermined beamspread and beam deflection angle; locating the additional substratematrix parallel to said first mentioned substrate matrix; and diffusingnon-diffused light from the first mentioned matrix through theadditional substrate matrix.
 10. A volume holographic diffusercomprising a matrix within a substrate having patterned nestedindividual joined geometrically shaped cells of holographic diffusersstructured for forming a combined superimposed resultant diffused lightbeam with an angular luminance distribution profile curve with sharplyvertical profile shapes and with a substantially flat and wide peak toproduce a uniform resultant luminance over a wide range of view with apredetermined beam spread and beam deflection angle in relation to alocation of view of the combined resultant diffused light beam.
 11. Thediffuser of claim 10 wherein said matrix has at least one holographicdiffuser which receives and diffuses at east one non-collimated lightbeam.
 12. The diffuser of claim 10 wherein the nested individual joinedgeometrically shaped cells are polygonal in shape.
 13. The diffuser ofclaim 10 wherein the nested individual joined geometrically shaped cellsare square in shape.
 14. The diffuser of claim 10 wherein the nestedindividual joined geometrically shaped cells are triangular in shape.15. The diffuser of claim 10 wherein the nested individual joinedgeometrically shaped cells are rectangular in shape.
 16. The diffuser ofclaim 10 wherein the nested individual geometrically shaped cells arehexagonal in shape.
 17. The diffuser of claim 10 further comprising anadditional matrix having patterned nested individual joinedgeometrically shaped cells of holographic diffusers structured forforming a combined resultant diffused light beam with an angularluminance distribution profile curve with sharply vertical profileshapes and with a substantially flat and wide peak to produce a uniformresultant luminance over a wide range of view with a predetermined beamspread and beam deflection angle in relation to a location of view ofthe combined resultant diffused light beam; and said additional matrixbeing located parallel to said first mentioned matrix and whereinnon-diffused light from said first mentioned matrix is diffused by saidadditional matrix.
 18. The volume holographic diffuser of claims 10wherein said individual joined geometrically shaped cells of holographicdiffusers are arranged in nested subgroups.
 19. A volume holographicdiffuser having individual cells for a display comprising displaypixels, said diffuser individual cells being clustered in a contiguousarrangement of nested cell subgroups, the size of each said subgroupbeing smaller than a display pixel.
 20. The volume holographic diffuserof claims 19 wherein said diffuser is directly attached to said display.